Electrical contact apparatus

ABSTRACT

Electrical contact apparatus for continuous, efficient and uniform application of high current to a moving wire or similar elongate element in a continuous electroplating process, and for mechanical guidance of such wire into a plating bath. A plurality of large area electrical contact members are biased toward and into intimate engagement with the wire and are flexibly mounted to enable positive uniform electrical contact to be maintained notwithstanding spurious motion and irregularities of the moving wire. The contact areas of the electrical contact members which confront the moving wire are configured to complement the confronting cross-sectional curvature of the wire, thereby providing a relatively large contact area for application of high current at low current density.

United States Patent [191 Hunt et a1.

[ ELECTRICAL CONTACT APPARATUS [75] Inventors: Robert E. Hunt, Andover; John Delahanty, Boston; Bruce M. Lane,

Bedford, all of Mass.

[73] Assignee: Arthur D. Little, Inc., Cambridge,

Mass.

22 Filed: Mar. 29, 1973 21 Appl. No.: 346,141

52 user ..307/145,339/9 51 Int. Cl. ..H01r4l/00 58 Field otSearch ..307/145;339/9 R,9A,

339/9 E, 9 RY; 219/155; 191/47, 48, 49, 50, 57, 59, 59.1, 60.1, 60.4

[ 1 Oct. 22, 1974 3,714,368 1/1973 Nautry et al. 339/9 R X Primary Examiner-Robert K. Schaefer Assistant Examiner-William J. Smith Attorney, Agent, or Firm-Weingarten, Maxham & Schurgin [57] ABSTRACT Electrical contact apparatus for continuous, efficient and uniform application of high current to a moving wire or similar elongate element in a continuous electroplating process, and for mechanical guidance of such wire into a plating bath. A plurality of large area electrical contact members are biased toward and into intimate engagement with the wire and are flexibly mounted to enable positive uniform electrical contact to be maintained notwithstanding spurious motion and irregularities of the moving wire. The contact areas of the electrical contact members which confront the moving wire are configured to complement the confronting cross-sectional curvature of the wire, thereby providing a relatively large contact area for application of high current at low current density.

14 Claims, 4 Drawing Figures 1 ELECTRICAL CONTACT APPARATUS FIELD OF THE INVENTION This invention relates to continuous electroplating apparatus and more particularly to electrical contact apparatus for the supply of high current to and the guidance along a travel path of a moving wire or other elongate element being plated.

BACKGROUND OF THE INVENTION In the continuous electroplating of wire or other filamentary or elongate elements, the wire is drawn through a plating bath while being maintained at a selected operating potential with respect to the bath. Since the wire is in motion through the bath, fixed electrical contact cannot be made to the wire and electrical contact must be made by apparatus which movably contacts the wire. The relative motion between the wire and the contact apparatus gives rise to significant difficulties, especially in plating systems where high current is employed. Momentary loss of contact between the contact apparatus and moving wire can result in electrical arcing which, in turn, can produce pitting and distortion of both the electrical contacts and the wire being plated. Loss of contact can also result in non-uniform plating.

Conventional systems for electroplating wire or other similar elements typically employ conductive rollers as electrical contacts. Such rollers are arranged to engage a surface of the wire and to rotate in response to longitudinal movement of the wire. A major deficiency inherent in the use of rollers as electrical contacts is the relatively small contact area between the moving wire and the rollers at any given time. Even if grooved rollers are employed to contact a greater portion of the wire surface, the contact area between the rollers and moving wire is still rather small. For a given current flow, the current density across a contact area is inversely proportional to the contact area, and, as a result, current density across a small contact area such as with roller contact, is relatively high. High current density also results in relatively high contact temperature, and operating current levels are thus limited by the current density which can be employed without melting. In addition, the small contact area of roller contacts can be sensitive to irregularities in the wire surface of spurious motion of the wire which can cause loss of electrical contact, with consequent arcing and its deleterious effects.

SUMMARY OF THE INVENTION In accordance with the present invention, contact apparatus is provided which is especially adapted for use in continuous plating systems and wherein relatively large area positive electrical contact is made to a moving wire or other elongate or filamentary element by a plurality of contact members which are biased into intimate engagement with the moving wire and which are configured and mounted to maintain contact even in the presence of spurious motion and surface irregularities of the moving wire. The novel contact apparatus can also serve to mechanically guide the wire along a defined path of travel. Briefly, a plurality of contact members are provided in confronting spaced relationship, each having a shaped portion complementary to the configuration of a moving wire adapted for movement of the wire between and in engagement with the contact members. Each contact member is biased into intimate engagement with the moving wire and is movable to accommodate spurious motion of the wire and surface irregularities which may be present, thereby to maintain continuous electrical contact. One or more of the contact members can be in fixed position along an axis transverse to the axis of travel to define the travel path and guide the wire in its movement therealong. A cooling fluid can be circulated through the contact members to maintain a predetermined operating temperature even at high operating currents. The effective contact area between the contact apparatus of the present invention and moving wire is relatively large to accommodate high currents at relatively low current densities across the contact areas. The invention also reduces the possibility of contact loss and resultant arcing which likely would occur.

DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation of a continuous plating system in which the invention is especially useful;

FIG. 2 is a pictorial representation of electrical contact apparatus according to the invention;

FIG. 3 is an elevation view of the contact apparatus of FIG. 2; and

FIG. 4 is a pictorial representation of an alternative contact member useful in the invention.

DETAILED DESCRIPTION OF THE INVENTION The electrical contact apparatus of the invention may advantageously be employed in processes for continuous electroplating of wire or other elongate or filamentary elements. Typical apparatus for the continuous electroplating of wire is illustrated schematically in FIG. 1, wherein a wire 10 is shown moving from left to right, as indicated by arrow 11, from a supply reel to a take-up reel (not shown). The wire first passes through a straightening device 12, typically a plurality of confronting rollers between which the wire is moved, and thence through a series of cleaning baths 14 for removal of grease and other surface contaminants. The wire is then pre-plated in a plating tank 16 with a suitable substrate coating which enhances the efficiency of subsequent plating. From the pre-plating tank, the wire is drawn into contact apparatus 18 after washing by a water or other suitable spray to remove grit or other foreign matter, which might otherwise interfere with electrical contact between the wire and the contact apparatus. The wire then is drawn through plating bath 20 which includes an anode structure 21. After emerging from the plating bath, wire 10 passes through contact apparatus 22 which is identical to contact apparatus 18. The contact apparatus 18 and 22 functions as the cathode of the plating system and together with anode structure 21 are operative in well known manner to effect plating of a conductive material from the plating solution in bath 20 onto the surface of wire 10.

The contact apparatus of the invention, shown generally at 18 and 22 in FIG. 1, for application of high current to a moving wire or similar elongate element is illustrated in detail in FIGS. 2 and 3. A wire 10 is disposed with respect to a stationary fixture 34 for movement in the direction indicated'by arrow 32. A contact member 36 is in electrical contact with the moving wire along a first side of the wire surface, while contact members 38, 40 and 42 maintain electrical contact with a second side of the wire. Typically, contact member 36 and contact members 38, 40 and 42 are positioned at respective opposite sides of the moving wire in order to guide and accurately position the wire as it proceeds from the contacts into an electroplating bath or other associated apparatus. The contact members are typically formed of a beryllium-copper alloy or other suitable material having the desirable conductive and thermal properties. Fixture 34 which serves to mount the operative components is typically constructed of an electrically insulative baseplate 35 and support plates 51 and 55 and stop blocks 64 and 66 of stainless steel.

. Contact member 36 is rotatably mounted on a yokeshaped member 44 by means of a pin 46 which extends longitudinally through the ends of the yoke and through an opening in contact member 36, thereby allowing rotation of member 36 with respect to yoke 44 about the axis defined by pin 46. Yoke 44 is attached to contact member 36 at a point forward along the direction of wire travel, of the longitudinal center of member 36, such that member 36 has a larger portion 37 at the end into contact with which the wire first moves, and a smaller end 39 on the opposite side of pin 46. The off center positioning of contact 36 with respect to yoke 44 is effective to compensate for frictional forces arising from motion between the moving wire and the contact member which can tend to produce rotation of member 36 about pin 46 and consequent unequal contact pressure. Contact members 38, 40 and 42 are similarly mounted off center for the same purpose.

Yoke 44 is rotatably mounted with respect to an adjustable mounting member 48 by means of a cylindrical pin 47 unitary with and extending from the yoke and which resides in a complementary cavity in mounting member48. Pin 47 is of sufficient length to prevent contact member 36 from becoming detached from member 48 in the absence of wire 10. Alternatively, a suitable stop mechanism may be employed to capture pin 47 within member 48 without impairing its rotatability. Mounting member 48 is, in the illustrated embodiment, of cylindrical form having a threaded portion 49 mating with a complementarily threaded hole 50 in upstanding plate 51 of fixture 34. By rotation of member 48 in hole 50, the position of contact member 36 along an axis transverse to the direction of motion of the wire can be adjusted to efine a reference position for the moving wire and thus define the travel path. The selected position of contact member 36 is secured by a locknut 52 which engages mounting member 48 and plate 51. The outer end 53 of mounting member 48 has a knurled circumferential surface to serve as a suitable grip for-adjustment. It will be appreciated that the invention also serves, as well as for electrical contact purposes, to guide the wire along its path of travel through the contact apparatus and into the plating bath. Transverse positioning of the wire is established and maintained by the adjusted disposition of contact member 36, and moving wire is urged into and guided along the defined travel path by action of the biased contact members 38, 40 and 42.

Contact members 38, 40 and 42 are rotatably mounted on respective piston shafts 54A, 54B and 54C which are coupled to associated pneumatic cylinders 56A, 56B and 56C, respectively, which are mounted to upstanding plate 55 of fixture 34. The precise mounting and configuration of contact member 38 will now be described in detail, it being understood that members 40 and 42 are similarly mounted and configured. The end of shaft 54A is provided with a rounded ball 57 which is inserted into a cavity 58 formed in contact member 38 and which cooperates therewith to serve as a ball joint allowing motion of member 38 along any axis. Ball 57 is retained in cavity 58 by a set screw 60 or other suitable means. As with the mounting of contact member 36 above described, cavity 58 in contact member 38 is positioned forward (along the wire travel direction) of the longitudinal center of the contact member to compensate for frictional forces and unequal contact pressure. Shaft 54A, which can be part of the piston of cylinder 56A or connected as a separate element thereto, biases contact member 38 into engagement with wire 10 and urges the wire into engagement with member 36. Pneumatic cylinder 56A and its associated piston allows sufficient piston travel to enable retraction of shaft 54A to permit installation of wire 10 into the contact apparatus and to permit detachment and replacement of contact member 38.

Contact members 40 and 42 are mounted identically as contact member 38, and pneumatic cylinders 56A, 56B and 56C are typically driven by a single air line providing a selected operating pressure and which maintains equal pneumatic pressure in the cylinders to thus provide an identical biasing force for each of the contact members 38, 40 and 42.

Referring now additionally to FIG. 3, it is seen that the contact members each have a grooved surface which confronts the moving wire. The confronting surfaces of the contact members are configured to com plement the curvature of the'confronting moving wire surfaces, thereby to provide intimate engagement between the moving wire and contact members and large area contact for maintaining relatively low current densities. If, alternatively, a wire or other element having a noncircular cross section is employed with the invention, contact members can be provided having confronting surface configurations to complement the respective confronting surfaces of the particular element. Bevels 62A, 62B, 62C and 62D can be provided on respective members 36, 38, 40 and 42 at the edges of the contacting grooved surfaces on the ends facing oppositely to the direction of wire motion to facilitate entry of the moving wire into engagement with the contacts and to minimize drag between the contact members and moving wire. Various bevel or chamfer configurations can of course be provided to suit specific implementations.

An alternative contact member construction is illustrated in FIG. 4 wherein arcuate grooves are provided in the contacting surface to collect dirt or other debris which may otherwise be drawn through the contacts. Referring to FIG. 4, a contact member is shown having a contact surface 82 for engagement of a moving wire. First and second grooves 84 are provided in surface 82 near respective ends of member 80 and disposed transversely of the longitudinal axis of member 80 along which the wire is moved. In use, dirt or other debris, such as may be on the wire surface, tends to collect in the grooves 84 rather than be drawn along the contacting surface, thereby to lessen wear on the contact surface and minimize interference with the electrical contact. The number and arrangement of grooves 84 can of course be varied tosuit specific implementations of the invention.

Contact members 36, 38, 40 and 42 can be cooled to a selected operating temperature by various cooling means, such as by a circulating liquid coolant. Passages 70 are provided longitudinally through each of the contact members for cooling purposes and flexible tubing 72 is provided to interconnect the passages in a serial path through which a suitable coolant is caused to flow. The tubing is sufficiently flexible and is positioned to not interfere with requisite movement of the contact members.

Each contact member is disposed in spaced relationship between a pair of stop blocks. As seen in FIG. 2, member 36 is disposed between stops 64A and 648, member 38 is disposed between stops 66A and 66B, while member 40 is disposed between stops 66B and 66C. Finally, member 42 is disposed between stops 66C and 66D. The surfaces of the stops confronting adjacent contact members are spaced therefrom to prevent excessive motion of the contact members in the direction of wire motion under extraordinary conditions, such as when frictional forces or surface irregularities in the :moving wire temporarily bind one or more contact member to the moving wire. The stops can also serve to restrict the extent of rotation of the contact members about their respective mountings. Thus, the stops can prevent bending or other distortion of the contact members or mountings.

Electrical current, which may typically be of the order of one thousand amperes is supplied from a suitable source to contact members 36, 38, 40 and 42 by means of respective leads 67A, 67B, 67C and 67D, and associated connectors 68A, 68B, 68C and 68D. The leads are constructed to be sufficiently flexible so as not to impede intended motion of the respective contact members and are usually connected to a bus bar or terminal block coupled to an energy source. The baseplate 35 of fixture 34 is of an electrically insulative material, such as fiberglass board, to isolate the contact apparatus from electrical ground. Mounting plates 51 and 55 and stops 64 and 66, which in the illustrated embodiment are conductive, are thus insulated from electrical ground and are electrically neutral. To the extent the contact members are in electrical connection with the associated conductive structure, this structure will be at substantially the same potential as the contact members. Alternatively, the entire contact apparatus can be maintained at substantially the same potential as the contact members such as by use of a conductive supporting baseplate which of course would be insulated from ground.

In summary of the operation of the invention, the biasing force of pneumatic cylinders 56A, 56B and 56C urges contact members 38, 40 and 42 forward to cause positive engagement of the moving wire or other ele ment between these contact members and confronting contact member 36, all of which have large area contacting surfaces of configuration complementary to the configuration of the moving wire. The biasing force exerted upon the contact members maintains the members in intimate engagement with the moving wire, while the contact members are movable to accommodate spurious motion of the wire and surface irregularities thereon which may be present, while achieving continuous large area electrical contact between all of the electrical contacts and the wire and guidance of the wire along its travel path. The configured surfaces of the contact members provide, in engagement with the moving wire, contact areas of relatively large size which enables a relatively large amount of current to be supplied to the moving wire at a relatively low current density.

While the contact apparatus of the invention has been described and is especially useful in the continuous electroplating of wire or other similar elements, it will be appreciated that the invention is also applicable to many other purposes in which continuous high current contact is to be made with a moving element. It will also be appreciated that variations in the implementation of the invention herein disclosed will occur to those skilled in the art, and accordingly it is intended that such variations be included within the scope of the present invention.

What is claimed is:

1. Electrical contact apparatus for application of high current to an elongated moving element and comprising:

mounting means;

at least one first contact member supported by said mounting means and having a contact surface in confronting sliding contact with said moving element on a first side of said element;

at least one second contact member supported by said mounting means and having a contact surface in confronting sliding contact with said moving element on a second side of said element substantially opposite to said first side;

said at least one first and second contact members being operative to guide said elongate moving element along a predetermined travel path; the electrical contact surface of each of said contact members comprising a shaped surface having a configuration complementary to the confronting surface configuration of said moving element;

biasing means operative to maintain said contact members in intimate engagement with said moving element;

electrical current supply means for conducting high current to said contact members; and

contact member supporting means operative to allow movement of said contact members with respect to said mounting means to accommodate spurious motion and irregularities of said moving element.

2. Electrical contact apparatus according to claim 1 wherein said at least one second contact member comprises contact members which are individually and separately biased by respective ones of said biasing means.

3. Electrical contact apparatus according to claim 1 further comprising a cooling system operative to maintain said contact members at a predetermined temperature.

4. Electrical contact apparatus according to claim 1 wherein said at least one first contact member is rotatably mounted with respect to an adjustably fixed point along an axis generally transverse to the longitudinal axis of said moving element to define a travel path for said moving element; and

wherein said biasing means is operative to urge said at least one second contact member toward said moving element, thereby to urge the moving ele-' ment into engagement with said first contact member.

5. Electrical contact apparatus according to claim 1 further comprising at least one stop block disposed adjacent at least one of said contact members and operative to restrict the motion thereof in directions along the axis of motion of said moving element.

6. Electrical contact apparatus according to claim 1 wherein said contact member supporting means includes means for attaching said contact members at a point longitudinally disposed forwardly of the longitudinal center of each of said contact members in the direction of motion of said moving element.

7. Electrical contact apparatus according to claim 1 wherein said contact member supporting means include means allowing universal rotation of at least one of said contact members with respect to said mounting means.

8. Electrical contact apparatus according to claim 1 wherein at least one of said contact members has a beveled edge on the end of said contact surface facing opposite to the direction of motion of said'moving element. I

9. Electrical contact apparatus according to claim 1 wherein at least one of said contact members includes arcuate grooves in the contact surface thereof and disposed transversely of the axis of motion of said moving element.

10. Electrical contact apparatus according to claim 1 and further including a plurality of stop blocks disposed with each of said contact members in spaced relationship between adjacent ones thereof thereby to restrict the displacement of said contact members along the axis of motion of said moving element.

11. Electrical contact apparatus for application of high current to an elongated moving element and comprising: I

mounting means electrically insulated from ground;

a first contact member having a contact surface in confronting sliding engagement with said moving element on a first side thereof;

a mounting member supporting said first contact member and adjustably affixed to said mounting means to determine the position of said first contact member along an axis generally transverse to the longitudinal axis of said moving element, thereby to determine a travel path for said moving element;

said mounting member including supporting means operative to allow universal movement of said first contact member with respect to said mounting member to accommodate spurious motion and irregularitiesof said moving element;

a plurality of second contact members each supported by said mounting means and having a contact surface in confronting sliding engagement with said moving element on a second side thereof substantially opposite to said first side;

the electrical contact surface of each of said contact members comprising a shaped surface having a configuration complementary to the confronting surface configuration of said moving element;

said mounting means including supporting means operative to allow universal movement of each of said second contact members with respect to said mounting means to accommodate spurius motion and irregularities of said moving element;

biasing means operative to maintain each of said second contact members in intimate engagement with said moving element and to maintain said element in intimate engagement with said first contact member along a predetermined travel path;

said biasing means including for each of said second contact members a pressurized cylinder supported by said mounting means and a piston cooperative with said cylinder to provide biasing force along a generally transverse axis relative to the longitudinal axis of motion of saidmoving element;

electrical current supply means for conducting high current to said contact members; and

stop means disposed adjacent to the ends of each of said contact members and operative to restrict the longitudinal displacement thereof.

12. Electrical contact apparatus according to claim 11 and further comprising:

cooling means including a fluid path having passages extending longitudinally through each of said contact members, and tubing serially interconnecting said passages whereby a liquid coolant can be circulated through said fluid path and is operative to maintain said contact members at a predetermined temperature.

13. Electrical contact apparatus for application of high current to an elongated moving element and comprising:

a base, electrically insulated from ground and including first and second upstanding mounting plates;

a first contact member having a contact surface in confronting sliding engagement with said moving element on a first side thereof;

a support member threadably engaging said first mounting plate at an adjustably fixed position along an axis generally transverse to the longitudinal axis of said moving element and supporting said first contact member at an adjustably fixed point thereby to determine a travel path for said moving element;

said support member being operative to allow universal movement of said first contact member with respect to said support member to accommodate spurious motion and irregularities of said moving element;

a plurality of second contact members each supported by said second mounting plate and having a contact surface in confronting sliding engagement with said moving element on a second side thereof, substantially opposite to said first side;

the electrical contact surface of each of said contact members comprising a shaped surface having a configuration complementary to the confronting configuration of said moving element;

biasing means for maintaining each of said second contact members in intimate engagement with said moving element and for maintaining said element in intimate engagement with said first contact member along a predetermined travel path;

said biasing means including for each of said second contact members a pressurized cylinder supported by said second mounting plate and a piston cooperative with said cylinder to provide biasing force along an axis generally transverse to the longitudinal axis of motion of said moving element;

said biasing means including support means operative to allow universal movement of each of said second contact members with respect to said support means to accommodate spurious motion and irregularities of said moving element;

electrical current supply means for conducting high current to said contact members;

stop means supported by said base and disposed adjacent to the ends of each of said contact members and operative to restrict the longitudinal displacement thereof; and

cooling means including a fluid path having passages extending longitudinally through each of said contact members, and flexible tubing serially interconnecting said passages whereby a liquid coolant can be circulated through said fluid path for maintaining said contact members at a predetermined temperature and without interferring with the free movement of said contact members.

14. Electrical contact apparatus according to claim 10 13 wherein at least one of said contact members includes arcuate grooves in the contact surface thereof and disposed transversely of the axis of motion of said moving element. 

1. Electrical contact apparatus for application of high current to an elongated moving element and comprising: mounting means; at least one first contact member supported by said mounting means and having a contact surface in confronting sliding contact with said moving element on a first side of said element; at least one second contact member supported by said mounting means and having a contact surface in confronting sliding contact With said moving element on a second side of said element substantially opposite to said first side; said at least one first and second contact members being operative to guide said elongate moving element along a predetermined travel path; the electrical contact surface of each of said contact members comprising a shaped surface having a configuration complementary to the confronting surface configuration of said moving element; biasing means operative to maintain said contact members in intimate engagement with said moving element; electrical current supply means for conducting high current to said contact members; and contact member supporting means operative to allow movement of said contact members with respect to said mounting means to accommodate spurious motion and irregularities of said moving element.
 2. Electrical contact apparatus according to claim 1 wherein said at least one second contact member comprises contact members which are individually and separately biased by respective ones of said biasing means.
 3. Electrical contact apparatus according to claim 1 further comprising a cooling system operative to maintain said contact members at a predetermined temperature.
 4. Electrical contact apparatus according to claim 1 wherein said at least one first contact member is rotatably mounted with respect to an adjustably fixed point along an axis generally transverse to the longitudinal axis of said moving element to define a travel path for said moving element; and wherein said biasing means is operative to urge said at least one second contact member toward said moving element, thereby to urge the moving element into engagement with said first contact member.
 5. Electrical contact apparatus according to claim 1 further comprising at least one stop block disposed adjacent at least one of said contact members and operative to restrict the motion thereof in directions along the axis of motion of said moving element.
 6. Electrical contact apparatus according to claim 1 wherein said contact member supporting means includes means for attaching said contact members at a point longitudinally disposed forwardly of the longitudinal center of each of said contact members in the direction of motion of said moving element.
 7. Electrical contact apparatus according to claim 1 wherein said contact member supporting means include means allowing universal rotation of at least one of said contact members with respect to said mounting means.
 8. Electrical contact apparatus according to claim 1 wherein at least one of said contact members has a beveled edge on the end of said contact surface facing opposite to the direction of motion of said moving element.
 9. Electrical contact apparatus according to claim 1 wherein at least one of said contact members includes arcuate grooves in the contact surface thereof and disposed transversely of the axis of motion of said moving element.
 10. Electrical contact apparatus according to claim 1 and further including a plurality of stop blocks disposed with each of said contact members in spaced relationship between adjacent ones thereof thereby to restrict the displacement of said contact members along the axis of motion of said moving element.
 11. Electrical contact apparatus for application of high current to an elongated moving element and comprising: mounting means electrically insulated from ground; a first contact member having a contact surface in confronting sliding engagement with said moving element on a first side thereof; a mounting member supporting said first contact member and adjustably affixed to said mounting means to determine the position of said first contact member along an axis generally transverse to the longitudinal axis of said moving element, thereby to determine a travel path for said moving element; said mounting member including supporting means operative to allow universal movement of said first contact member with respect to said mounting member to accommodate spurious motion and irregularities of said moving element; a plurality of second contact members each supported by said mounting means and having a contact surface in confronting sliding engagement with said moving element on a second side thereof substantially opposite to said first side; the electrical contact surface of each of said contact members comprising a shaped surface having a configuration complementary to the confronting surface configuration of said moving element; said mounting means including supporting means operative to allow universal movement of each of said second contact members with respect to said mounting means to accommodate spurius motion and irregularities of said moving element; biasing means operative to maintain each of said second contact members in intimate engagement with said moving element and to maintain said element in intimate engagement with said first contact member along a predetermined travel path; said biasing means including for each of said second contact members a pressurized cylinder supported by said mounting means and a piston cooperative with said cylinder to provide biasing force along a generally transverse axis relative to the longitudinal axis of motion of said moving element; electrical current supply means for conducting high current to said contact members; and stop means disposed adjacent to the ends of each of said contact members and operative to restrict the longitudinal displacement thereof.
 12. Electrical contact apparatus according to claim 11 and further comprising: cooling means including a fluid path having passages extending longitudinally through each of said contact members, and tubing serially interconnecting said passages whereby a liquid coolant can be circulated through said fluid path and is operative to maintain said contact members at a predetermined temperature.
 13. Electrical contact apparatus for application of high current to an elongated moving element and comprising: a base, electrically insulated from ground and including first and second upstanding mounting plates; a first contact member having a contact surface in confronting sliding engagement with said moving element on a first side thereof; a support member threadably engaging said first mounting plate at an adjustably fixed position along an axis generally transverse to the longitudinal axis of said moving element and supporting said first contact member at an adjustably fixed point thereby to determine a travel path for said moving element; said support member being operative to allow universal movement of said first contact member with respect to said support member to accommodate spurious motion and irregularities of said moving element; a plurality of second contact members each supported by said second mounting plate and having a contact surface in confronting sliding engagement with said moving element on a second side thereof, substantially opposite to said first side; the electrical contact surface of each of said contact members comprising a shaped surface having a configuration complementary to the confronting configuration of said moving element; biasing means for maintaining each of said second contact members in intimate engagement with said moving element and for maintaining said element in intimate engagement with said first contact member along a predetermined travel path; said biasing means including for each of said second contact members a pressurized cylinder supported by said second mounting plate and a piston cooperative with said cylinder to provide biasing force along an axis generally transverse to the longitudinal axis of motion of said moving element; said biasing means including support means operative to allow universal movement of each of said second contact members with respect to said support means to accommodate spurious motion and irregularities of said Moving element; electrical current supply means for conducting high current to said contact members; stop means supported by said base and disposed adjacent to the ends of each of said contact members and operative to restrict the longitudinal displacement thereof; and cooling means including a fluid path having passages extending longitudinally through each of said contact members, and flexible tubing serially interconnecting said passages whereby a liquid coolant can be circulated through said fluid path for maintaining said contact members at a predetermined temperature and without interferring with the free movement of said contact members.
 14. Electrical contact apparatus according to claim 13 wherein at least one of said contact members includes arcuate grooves in the contact surface thereof and disposed transversely of the axis of motion of said moving element. 